By Nicole Garneau, PhD

First it was the tongue, then the guts, then the lungs,
now researchers have found evidence that there are bitter taste
receptors in the brain! Why? The scientists think that the
activation of bitter taste receptors in the brain increases calcium
in brain cells and this increase in calcium leads to the production
of chemicals in the brain that regulate food intake.

Questions to think about:

1. What is the actual ligand (the bitter
chemical/molecule) in the brain that activates the taste receptors?
This study uses quinine as a ligand to prove that the cells are
there and can be activated, but the scientists add the quinine
specifically to see if the cells react.

2. What concentration of the ligand really needs to occur
naturally in the brain for the receptors to be activated? There is
proof that quinine can cross the blood brain barrier, so if the
ligand is quinine, how much needs to be around for the brain cells
to be activated by it?

3. What is the true physiological affect of having brain
cells express taste receptors that can be activated by bitter
compounds? Scientists would need to do experiements that study
behavoir to know if the activated cells either stimulate or block
food consumption.

3. This study was done in rats, would scientists find the
same receptors in human brain cells? Does this affect how much
we eat?